ICU patients will be enrolled as soon as possible but no later than 12 hours after fulfilling the criteria for randomisation. Patients will be allocated in a 1:1 ratio to either the treatment group, receiving intravenous Vitamin C (1.5g every 6 hours), Thiamine (200mg every 12 hours) and Hydrocortisone (50mg every 6 hours), or to the control group, receiving Hydrocortisone (50mg every 6 hours) alone.